A sentence with an em dash, a curly quote, or a non-breaking space is not evidence that a
language model wrote it. Publishers, typesetters, and copyeditors have set these marks —
deliberately, and by locale-specific convention — since long before any language model existed.
Reading them as an "AI tell" mistakes a craft that predates the technology for a fingerprint it
left behind.
That misreading has a cost. When correct punctuation gets treated as suspicious, writers get
pushed toward flatter, safer punctuation to avoid the accusation — the wrong incentive, aimed at
the wrong target.
Polytypo exists because the craft underneath is mechanical, well documented, and worth
automating correctly: quotes, dashes, ellipses, apostrophes, symbols, and no-break spaces,
applied the way a locale's own style guide — Duden, Imprimerie nationale, Kotus, Chicago,
Мильчин — actually specifies them, not the way one universal style would guess.
Not one universal style
Correct typography isn't an "AI style." It's several different, locale-specific ones.
Every card below runs the exact same input string through transform(). Only the
locale changes; quote style, dash style, and spacing all follow.
Input, unchanged
She asked, "Isn't this the shop they call 'round the corner'?" ... We'd walked - nearly 3 km - just to find it closed. Copyright (c) 2026; the print measures 40x60 cm.